Primary and secondary stroke prevention in atrial fibrillation.

Atrial fibrillation, with a prevalence of 6% in those over 65 years, is responsible for 75-100 x 10(3) strokes each year in the United States. These strokes are more severe and have less favorable long-term prognosis than strokes due to other mechanisms. Modern trials show that warfarin reduces stroke rate by about 70% and aspirin by about 20%. Although average annual stroke rate among atrial fibrillation patients is about 4-5%, considerable risk heterogeneity exists. The goal of risk stratification is to differentiate patients with risk high enough to justify warfarin from those whose risk is so low that they are better off on aspirin or even no antithrombotic therapy. Ideal antithrombotic therapy is individualized, balancing risks of thromboembolism versus bleeding on antithrombotic therapy, and considering patient preferences. Although the science has advanced significantly in the past decade, application has lagged behind. Much benefit will potentially accrue from broad education efforts.